To think DS is being thoughtless

My DS is 11. Tomorrow there's an event happening at school and a few friends have arranged to go. The original plan half an hour ago when leaving his friend was for DS to walk round for him and go together at 10.00. He's now come home and after 30 seconds on the X Box has decided he's going with another friend at 11.00 (this friend lives further away and can't get to ours until then). We and the original friend live very close to the school. He says he just doesn't want go any earlier and the first friend was going at that time to help out. Although they'll all meet up eventually, I'm trying to explain to him how he could hurt his first friends feelings, but he doesn't seem to think so. AIBU to feel disappointed in what he's doing or am I overreacting considering they're 11?

He's now spoken to X who has to go at 10.00. He seems okay with it, and seems to have someone else going with him now anyway, so no harm done, hopefully. And it means Y doesn't have to go on his own at 11.00.

But I am disappointed that my DS didn't even consider how that was unfair, and still disagrees when I told him it's exactly the type of thing that would bother him if things were reversed.

In all honesty that's the sort of thing that happens to dd1. She would be X, and would sound fine about it, but come off and be pretty upset because she'd know that she is only useful until a better offer comes through.She'd go at 10, and probably see the other pair and not have the confidence to join in because she would feel if she was second best she'd be intruding.Sorry to sound harsh, but that's a reality for many children.

Why couldn't he go at 10, and say to the other boy to text when he arrives and they'd both meet him.